The present invention relates to the construction of intake pipes for supplying air and fuel to combustion chambers of an internal combustion engine.
In conventional intake pipes, an air swirl is positively created in combustion chambers of an internal combustion engine in order to increase the efficiency of combustion. However, a high speed air flow may be produced by an intake air deflection unit provided to form the air swirl. If the fuel jet is deflected and it impacts the surface of the walls of the intake pipe and the combustion chamber, a liquid film is formed on the wall surface. Therefore, unburned fuel may remain after combustion. As a result, the emission of hydrocarbons increases.
Further, there have been attempts to decrease the fuel consumption by using a lean burn in which the rate of the air to fuel (A/F ratio) is large. However, in an engine wherein a liquid film is formed on the combustion chamber wall, the efficiency of combustion is low, a stable lean burn condition can not be obtained, and the fuel consumption can not be improved.